Cefuroxime axetil is an antibiotic effective against a wide spectrum of microorganisms when administered orally.
Solid compositions for oral administration comprising cefuroxime axetil are presently available commercially in the form of tablets, and as powders for oral suspension.
There are substantial difficulties in the production of satisfactory solid compositions comprising cefuroxime axetil.
One problem is that it is difficult to make compositions for oral administration which provide high bioavailability; that is to say, that are well absorbed from the gastrointestinal tract into systemic circulation. In particular, if the cefuroxime axetil is in crystalline form, it exhibits poor water solubility and hence poor absorption.
U.S. Pat. No. 4,820,833 discloses that absorption can be improved by using cefuroxime axetil in pure amorphous form instead of crystalline form.
U.S. Pat. No. 4,897,270 further discloses that absorption from film coated tablets can be improved by formulating the tablets such that, when a tablet is ingested, the film coating ruptures rapidly in the gastrointestinal fluid, and the core then disintegrates immediately.
Canadian patent no. 2209868 discloses that, instead of using cefuroxime axetil in pure amorphous form, excellent dissolution and absorption can also be achieved by using cefuroxime axetil in the form of a co-precipitate of cefuroxime axetil and a water-soluble excipient.
A second problem in formulating satisfactory solid compositions comprising cefuroxime axetil is that cefuroxime axetil is relatively unstable in the presence of many common excipients (i.e. inactive ingredients) used to make solid pharmaceutical compositions.
The object of the present invention is to provide a means of stabilizing cefuroxime axetil, so as to reduce the rate of degradation of cefuroxime axetil in solid pharmaceutical compositions.
It has been surprisingly found that cefuroxime axetil can be stabilized by admixture with a zinc salt, preferably zinc chloride.
Compositions of the present invention will thus be solid pharmaceutical compositions comprising cefuroxime axetil as active ingredient and a zinc salt as stabilizer.
The amount of zinc salt in the composition will preferably be from about 0.1 to about 4 parts per 100 parts cefuroxime axetil by weight; more preferably from about 0.2 to about 2 parts per hundred parts cefuroxime axetil by weight; and most preferably about one part per hundred parts cefuroxime axetil by weight.
In order to enable maximum bioavailability, the cefuroxime axetil in the composition will preferably be in pure amorphous form or in the form of a co-precipitate with a water-soluble diluent.
The zinc salt may be added to the composition at any point in the process of production of the composition.
However, when the cefuroxime axetil is used in pure amorphous form or in the form of a co-precipitate, the zinc salt will preferably be added, in the process of making the pure amorphous cefuroxime axetil or the co-precipitate, in order to get a more intimate mixture of the zinc salt with the cefuroxime axetil.
In the case of pure amorphous cefuroxime axetil, the process of manufacture will preferably be to dissolve the zinc salt along with the cefuroxime axetil in suitable solvent and then evaporate the solvent, preferably by spray-drying, in order to produce amorphous material comprising cefuroxime axetil and a small amount of zinc salt intimately mixed therein.
Similarly, in the case of a co-precipitate, the process will preferably be to dissolve the cefuroxime axetil, water-soluble diluent, and zinc salt together in suitable solvent and evaporate the solvent, again preferably by spray-drying to produce an amorphous co-precipitate comprising the cefuroxime axetil, water-soluble diluent, and zinc salt.
The amorphous material comprising cefuroxime axetil and zinc salt, or cefuroxime axetil, water-soluble diluent, and zinc salt, will then be further processed into the final solid composition which, as aforesaid, may be a tablet, or a powder or granules for oral suspension; that is to say, powder or granules to which water is to be added to provide a suspension for pediatric use.